The following abbreviations are utilized herein:
3Gthird generation (cellular standard)GSMglobal system for mobile communicationsHSDPAhigh speed downlink packet accessMACmedium access controlMRCmultiradio controllerRFradio frequencySDRsoftware defined radioSIMsubscriber identity moduleWLANwireless local area network (IEEE 802.11 family)
Traditionally, a radio access protocol stack has been a single entity with a top-level control interface and dedicated hardware resources. Having two instances of the same radio system in the same device has not been feasible in a practical sense, as this would require that two instances of all of the hardware and software resources be present.
It is recognized that some radio standards allow quite efficient de-coupling of the physical layer (PHY) and the protocols part (layers above PHY, such as the MAC). This may be used to share the same physical layer implementation between variants of one radio standard, or even across multiple standards. GSM and 3G resource sharing is one example, wherein the radio systems may utilize many of the same hardware resources efficiently since their standardization is coordinated in the same standardization body. This only allows, however, utilizing different radio access technologies to obtain access to the wireless cellular network, one technology at a time.